A centrifugal impact rock crusher is a device that accepts large size rocks, for example rocks approximately 2-5 inches in diameter, and breaks them apart into small, pieces, such as pieces approximately 1 inch or less in diameter. In operation, large rocks are fed downwardly through a hopper and feed tube and onto a feed cone at the center of an impeller turntable. A series of spaced impeller blades or members are positioned along the periphery of the turntable just off the feed cone. After landing on the feed cone, the rocks are deflected radially outwardly off of the feed cone and into the path of the rotating impellers. The impellers catch the rocks and throw them with tremendous centrifugal force radially outwardly and violently against fixed anvils. The turntable is positioned inside a large cylindrical housing that has a ring of anvils fixedly mounted along the inside of the housing wall in vertical alignment with the impellers. When the rocks strike the anvils, they crack under their own momentum into relatively uniform, often cubical, pieces and freely fall down onto a conveyor or other suitable output device, such as a receptacle.
The impeller blades of prior art rock crushers are generally wedge-shaped rectangular blocks that are mounted to the turntable with their narrow wedge ends adjacent or even partially overlapping the feed cone and their wide ends at the outer edge of the turntable. The purpose of the impellers is not to break apart the rocks, but to catch or grab the rocks and throw them outwardly against the anvils, which are fixedly mounted along the circumferential wall surrounding the turntable. While the anvils are designed to withstand tremendous impact forces, the impellers are mainly designed to withstand abrasion forces associated with slinging of the rocks outwardly against the anvils. Abrasion is caused not only by the rocks themselves, but also by the "fines" associated with the rocks. Fines includes dust and sand particles, dirt and mud, smaller rock fragments all of which may be carried by the large rock pieces into the rock crushing device.
It has been proposed to reduce wear on the impellers by creating a pocket within the impact or wear surface of the impeller. With pocketed impellers, fines collect in the pocket and thereby create a renewable wear surface of fines that contacts the rocks. As the rocks are slung by the impellers, the rocks sweep away a portion of the fines from the pocket. However, additional fines carried by the rocks subsequently refill the pocket. Canica-Jaques of Vancouver, Wash., U.S.A., for example, makes a rock crusher impeller with two radially adjacent pockets in the impeller wear surface. This type of rock crusher impeller, however, is limited in the size and type of rock that it can crush--rocks no larger than about 21/2 inches in diameter and relatively soft rock, such as limestone, cement, sulfur, etc. are best suited for crushing using the Canica-Jaques pocketed impellers. The Canica-Jaques'impellers also require rock material with a high fines content in order to replace the fines swept out of the pockets by the rocks, and with high moisture content in order to help hold the fines in the pockets.
However, prior art pocketed impellers have not been found to work satisfactorily with certain types of rock, namely, large, relatively hard and dry rock material. The present invention is designed to address these limitations of prior art centrifugal impact rock crusher impellers.